Multimedia Software Systems CS451

Transcription

1 Multimedia Software Systems CS451 Introduction to Multimedia What is Multimedia? What is multimedia? multi + media Multi (multus) : numerous Media : means that conveys something such as information From wikipedia.org: Multimedia is the use of several different media to convey information (text, audio, graphics, animation, video, and interactivity). In our class, Multimedia : the use of several different digitized computer media (text, audio, graphics, animation, video, etc) to convey information. 1

2 Inherent Properties of Multimedia Mixture of different media types Digital always Voluminous (Multimedia data is huge) Interactive (data contact human) Synchronization Real - time => Understanding these properties is important to design good multimedia applications. Three Processes that are Inherent to Multimedia Systems Multimedia content creation or multimedia authoring The process involves digitizing media ( audio, images, video) using capture devices and assembling/ processing them using smart software and hardware Storage and compression The process mostly involves state- of- the- art compression algorithms and standards for audio, video, images, and graphics. Distribution Distribution involves how multimedia content is distributed via various media, such as wired cables, optical networks, satellite, wireless networks, or any combination thereof, to specific platforms ranging from television, computers, personal digital assistants (PDAs), and so on. 2

3 Media Types Current Media Types Text Images Video (Movies, Documentaries, ) 2D/3D Graphics (Computer Object) Moving graphics (games, animation) Audio (Speech, Music, MIDI music) Future Media Types? Text text is a simple media that contains words to express something This is a line of text to explain that text does convey information with a hyperlink example! Hypermedia vs. Multimedia Hypertext : a user interface paradigm for displaying documents which contain automated cross-references to other documents called hyperlinks. Hypermedia: Hyperlinks also referring other than text Hypermedia is an application of multimedia. 3

4 Images Captured picture or computer generated (synthesized) picture Image In the form of a spatial two dimensional array Width and height Consists of individual elements called pixel Pixel depth (or bit depth) : 1,2,4,8,16,24 bits No particular structure other than pixel Video How do you describe video? Moving images Collection of frames Frame rates : number of frame displayed per second (fps) Aspect ratio : ratio of width to height Scanning format: interlaced or progressive No particular structure other than pixel/frame number 4

5 2D Graphics/3D Graphics Computer generated object Vector Graphics, 2D Sprites, etc Contains structure and they are revisable meaning editable Animation Computer generated movie Can be represented by a set of objects and timedependent directives (programs to be executed at playtime) Compactness and revisable Requires processing power for the playback 5

6 Audio How do you describe audio? Waveform, structure, Properties Sampling rate in hertz : # of samples per second Sample size: number of bits per sample Dimensionality: number of channels (mono or stereo) Frequency range or frequency band (narrow band voice vs. wide band music) Audio Media is of various kinds Speech Non-speech sound MIDI (Structured Audio) Multimedia System Classifications Static vs Dynamic Content change within a certain finite time (e.g. image vs video) Real time vs Orchestrated (e.g live broadcast vs DVD) Linear vs Non-linear (e.g hypermedia) Person-to-Person vs Person-to-Machine (e.g video conferencing vs CD-ROM) Distribution Single user (CD ROM and Computer) Peer to Peer (Teleconferencing between two addresses) Peer to Multi-Peer (Internet, Corporate Networks) Broadcast (Cable Network) 6